Method for treating phosphate material



iUN T o STATES,

Patented July 28, 1931 PATENT OFFICE STEWART :r. LLoYn AND ABsALoM MASON KENNEDY, F UNIVERSITY, ALABAMA, AssIG oR-s TO CHEMICAL PRODUCTS COMPANY, A CORPORATION or FLORIDA No Drawing. i

METHOD FOR TREATING PHOSPHATE MATERIAL This application is a continuation in part of our application, Serial No. 171,720, filed February 28, 1927. I a 1 This invention relates to armethod for treating phosphatematerial, such as phosphate rock, to produce a concentrated, soluble fertilizer containing nitrogen and phosphorusand has forits object the production 7, of such fertilizer directly from insoluble nomical maner. I I

A further object of our invention is to provide a cyclic process for the production of ammonium phosphate wherein provision is made for the use and regeneration ofthe reacting agent employed.

A still further object of our invention is to free the phosphate content of the raw ma: terial acted upon with an agent which is conserved and regenerated during each cycle of'operation. j

Anotherobject of our invention is to prophosphate material, in a simple and ecovide, in a process of the character designated,

a means whereby phosphates and sulphates in solutionare efiiciently and economically separated. a

Ammonium phosphate, as a concentrated,

soluble fertilizer containlng nitrogen and phosphorus, is recognized as havinga number of advantages, among which are that .it is thoroughly soluble in water,is not hygroscopic,contains a high percentage of plant food, mixes well with other fertilizer materials Q and maybe easily granulated or'reducedto a form which can'be readily handled by the "usualfertilizer distributers. Its

commercial production as afertilizer has heretofore-been seriously limited, however,

with phosphoric acidwhich was liberated from the raw material by one of the following methods: a

. I Ohemz'caZ processe The phosphate content of the insoluble raw material, such as'phosphate rock, was displaced by substitution .with another acid, such as sulphuric, and the Application filed May a1, 192s. Serial No. 279,616.

phosphoric acid thus liberated was then separated from the insolubles accompanying it and was concentrated and stored.

Volatz'lz'zatz'on process-The phosphate content of the raw material was liberated as phosphorus by heat in an electric or fuel fired furnace and collected, either in the form of phosphorus or, with an electrostatic precipitator, in the form of concentrated phosphoric acid produced by the action of air and moisture on the phosphorus in the furnace. If collected as phosphorus, this was converted into phosphoric acid by the action of steam or of air.

These processes require the expenditure of either a considerable quantity of sulphuric acid, or of electric energy, or fuel, and the separation, collection and storage of phosphorus or of phosphoric acid is somewhat difiicult and is expensive.

We have found that the expenditure of acids, energy or fuel and the separation, collection and storage of phosphoric acid, together with the subsequent operation of mixing this acid with ammonia may be avoided and that ammonium phosphate may be produced directly and more economically from the natural phosphate material in the following manner:

02 3 g i 302180 3 (NIL) 211 1 0 The precipitate is separated from the solution and an excess of ammonia is added to the latter whereupon the phosphate con-' tent is precipitated as relatively insoluble tri-ammonium phosphate, the sulphate content remaining in solution as ammonium sulphate, which reaction may be represented as follows a (NIL) zsoimmm sroi.

Theprecipitate of calcium sulphate from reactiontl) is digestedwith ammonium carbonate or its equivalent and by the following known reaction ammonium sulphate is formed in solution and calcium carbonate as a precipitate:

The ammonium sulphate solutions from Reactions (2) and (4) are collected, are evaporated and the resultant crystals are heated to about 300 C. when ammonia is driven off and collected and ammonium bisulphate isjformed' for-reuse with a fresh batch of raw material as follows: i

l 2SO4$ I I 6N:ELHSQ 6NH .It will be observed that in the production ofammonium phosphate by this process, the ammomum bisulphate 1s not expended but 1s amno ros usedover and over again, being regenerated in each cycle of operation of the process.

When consldered separately and by themselves, we are. aware that some of the steps 7 of our process have-heretofore beenidisclosed. For example, Step No. 1, lITWlllCh acid sulphates are caused to react on phosphate rock, has heretofore been taught, the specific substance and the proportions we employ, however, give a far better result than any heretofore known and, so far as we areaware, are entirely newI i Step No. 3, in which tri-ammonium phosphate is heated and converted into dior mono-ammonium phosphate, is known in the art, as are Step No. 4-, in which ammonium sulphate is produced by the reaction of a solution containing ammonium'carbonate on calcium sulphate, and Step Noni), in which ammonium sulphate is heated to form ammonium' bisulphate.

Step No.2, in which an excess of ammonia 1S caused to react one solution containing ammonium sulphates and phosphates for the :muna nro eung purpose of separating the phosphates from the sulphates, is, so far as we are aware, entirely novel, and provides a ready economical means for separating the phosphates from the sulphates, whereas, heretofore, the latter have gone into the final product as useless material.

The combination of steps for obtaining ammonium phosphate directly from phosphate rock, as herein described, has not,-so fas as we are aware, heretofore been-known or used. It will be apparent that the process embodies in this combination of steps greatly reduces the cost of manufacture in that the only raw materials required are phosphate rock, carbon dioxideand ammonia; The acid used in the process being-conserved and reused in a cycle and the expediture of electric energy or fuel beingeliminated I In practice. we prefer to proceed as fol lows: a 7

The natural phosphate,as phosphate rock, is pulverized and is mixed with water in a vessel provided with an agitator. To each 310 parts of phosphate rock corresponding to Ca (PO is added approximately 'ZOO parts of ammonium bis-ulphate, preferably in molten form as that produced in a subsequent operation; The mass is kept agitated until the reaction is substantially completed when the precipitate,- which consists of cal cium sulphate and the insolubles present in the raw material, is separated by filtration or by decanta tio-nfrom the solution containing soluble" sulphates and phosphates;

To this solution is added an excess of ammoniacomprising at least sixparts for each equivalent of P O in the solution, when the soluble sulphates and phosphates will beseparated, the latter as a precipitate ofi tri-calcium phosphate which is relatively insoluble in the solution of ammoniumsulp hate. This reaction is exothermic and is best performed in a vessel provided with a means for absorbing the heatgenerated.

What weclaim is 1. A. cyclic process for the productionof ammonium phosphate; from tricalcinm phosphate which consistsin treating the phosphate material with atleast six parts of am monium bisulphate, for each equivalent of P 0 in the phosphate material and separating the resulting calcium sulphate'as precipita te from the solution, treating the solution with at least six parts of ammonia to each 1;

equivalent of P 0 in the solution to form triammonium phosphate and to separate the phosphates from the sulphates contained in solution, and treating the sulphates to form ammonium bisulphate for reuse in the cycle.

2. A cyclic process for the production of ammonium phosphate from tricalcium phosphate which consists in treating the phosphate material with suflicient ammonium bisulphate to form with the base insoluble cali9 t-ures.

cium sulphate and separating the sulphate of the base as precipitate from the solution, treating the solution with an excess of ammonia to form triammonium phosphate and to separate the phosphates from the S111? phates contained in the solution, subjecting the triammonium phosphate to heat to drive ofl ammonia therefrom, digesting the calcium sulphate resulting from the first reaction with ammonia and carbon dioxide to form a precipitate of calcium carbonate and a solution containing ammonium sulphate,

and evaporating the ammonium sulphate so- 'lutions and heating the resulting crystals to form ammonium bisulphate for reuse in the cycle.

3. A cyclic process for the roduction of ammonium phosphate from a p osphate of a base which forms an insoluble sulphate, which consists in treating the phosphate ma terial with six parts of ammonium bisulphate to each equivalent of P 0 in the phosphate and separating the sulphate of the base as precipitate from the solution, treating the solution with at least six parts of ammonium for each equivalent of P 0 in the solution to separate the phosphates from the sulphates contained therein, subjecting the phosphate to heat to drive ofi ammonia therefrom and collecting the ammonia digesting the calcium sulphate resulting rom the first reaction with ammonia and carbon dioxide to form a precipitate of calcium carbonate and a solution containing ammonium sulphate, and evaporating the ammonium sulphate solutions and heatin the resulting crystals to form ammonium isulphate for reuse in the cycle.

In testimony whereof we aflix our signa- STEWART J. LLOYD. ABSALOM'MASON KENNEDY. 

